Heretofore the joint for connecting a crop cutting sickle to its drive arm has been effected by a pivot pin or bolt whose shank extends through a bore in the drive arm and also through the inner raceways of a pair of aligned antifriction bearings carried by the sickle bar. In such prior constructions, the connection between the pivot bolt and the drive arm relies primarily on friction achieved by the axial clamping force, produced by tightening the nut on the pivot bolt, to resist side-to-side movement between the drive arm and the pivot bolt. If the bolt loosens to any appreciable extent, the connection between the bolt and arm becomes loose and a rapid deterioration of the joint occurs.